Nanostructures Increase Water Droplet Adhesion on Hierarchically Rough Superhydrophobic Surfaces

Langmuir ◽  
2012 ◽  
Vol 28 (6) ◽  
pp. 3138-3145 ◽  
Author(s):  
Hannu Teisala ◽  
Mikko Tuominen ◽  
Mikko Aromaa ◽  
Milena Stepien ◽  
Jyrki M. Mäkelä ◽  
...  
Keyword(s):  
Water Droplet ◽  
Superhydrophobic Surfaces

scholarly journals Water droplet friction and rolling dynamics on superhydrophobic surfaces

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Matilda Backholm ◽  
Daniel Molpeceres ◽  
Maja Vuckovac ◽  
Heikki Nurmi ◽  
Matti J. Hokkanen ◽  
...  
Keyword(s):  
Contact Angle ◽  
Friction Force ◽  
Water Droplet ◽  
Superhydrophobic Surfaces ◽  
Silicon Surfaces ◽  
Force Sensors ◽  
Water Droplets ◽  
Indirect Contact ◽  
Gold Standard Method ◽  
Superhydrophobic Coatings

Abstract Superhydrophobicity is a remarkable surface property found in nature and mimicked in many engineering applications, including anti-wetting, anti-fogging, and anti-fouling coatings. As synthetic superhydrophobic coatings approach the extreme non-wetting limit, quantification of their slipperiness becomes increasingly challenging: although contact angle goniometry remains widely used as the gold standard method, it has proven insufficient. Here, micropipette force sensors are used to directly measure the friction force of water droplets moving on super-slippery superhydrophobic surfaces that cannot be quantified with contact angle goniometry. Superhydrophobic etched silicon surfaces with tunable slipperiness are investigated as model samples. Micropipette force sensors render up to three orders of magnitude better force sensitivity than using the indirect contact angle goniometry approach. We directly measure a friction force as low as 7 ± 4 nN for a millimetric water droplet moving on the most slippery surface. Finally, we combine micropipette force sensors with particle image velocimetry and reveal purely rolling water droplets on superhydrophobic surfaces.

scholarly journals Thermo-Responsive Water Droplet Adhesion on Superhydrophobic Surfaces

2013 ◽  
Vol 64 (1) ◽  
pp. 26-30 ◽  
Author(s):  
Daisuke ISHII ◽  
Akihito TAKAHASHI ◽  
Masatsugu SHIMOMURA
Keyword(s):  
Water Droplet ◽  
Superhydrophobic Surfaces

How to repel hot water from a superhydrophobic surface?

2014 ◽  
Vol 2 (27) ◽  
pp. 10639-10646 ◽  
Author(s):  
Zhe-Jun Yu ◽  
Jieyi Yang ◽  
Fang Wan ◽  
Quan Ge ◽  
Long-Lai Yang ◽  
...  
Keyword(s):  
Water Droplet ◽  
Superhydrophobic Surface ◽  
Hot Water ◽  
Superhydrophobic Surfaces ◽  
Surface Temperatures

We demonstrated the superhydrophobicity of five superhydrophobic surfaces by manipulating water droplet and surface temperatures.

Reply to Comment on Water Droplet Motion Control on Superhydrophobic Surfaces: Exploiting the Wenzel-to-Cassie Transition

Langmuir ◽  
2011 ◽  
Vol 27 (22) ◽  
pp. 13962-13963 ◽  
Author(s):  
Guangming Liu ◽  
Andrei Rode ◽  
Lan Fu ◽  
Vincent S. J. Craig
Keyword(s):  
Motion Control ◽  
Water Droplet ◽  
Superhydrophobic Surfaces ◽  
Droplet Motion

How Nanostructures Affect Water Droplet Nucleation on Superhydrophobic Surfaces

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Abulimiti Aili ◽  
QiaoYu Ge ◽  
TieJun Zhang
Keyword(s):  
Water Droplet ◽  
Superhydrophobic Surfaces ◽  
Experimental Investigations ◽  
Nucleation Density ◽  
Moderate Increase ◽  
Droplet Shape ◽  
Energy Applications ◽  
Cassie State ◽  
Droplet Nucleation ◽  
Surrounding Areas

Nucleation is the first stage of phase change phenomena, including condensation on nanostructured superhydrophobic surfaces. Despite plenty of theoretical studies on the effect of nanostructure density and shape on water droplet nucleation, not many experimental investigations have been reported. Here, we show both experimentally and theoretically that a moderate increase in the nanostructure density can lead to an increase in the nucleation density of water droplets because of the decreased energy barrier of nucleation in cavities formed between the nanostructures. Specifically, we observed droplets aligned in regions with denser nanostructures. The number and average volume of the aligned droplets in these regions were larger than that of the droplets in the surrounding areas. However, nucleation in cavities subsequently caused initial pinning of the droplet base within the nanostructures, forming a balloonlike, slightly elongated droplet shape. The dewetting transition of the pinned droplets from the Wenzel state to the unpinned Cassie state was predicted by quantifying the aspect ratio of droplets ranging from 3 to 30 μm. Moreover, the coalescence-jumping of droplets was followed by a new cycle of droplet condensation in an aligned pattern in an emptied area. These findings offer guidelines for designing enhanced superhydrophobic surfaces for water and energy applications.

Effects of Surface Topography and Colloid Particles on the Evaporation Kinetics of Sessile Droplets on Superhydrophobic Surfaces

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Wei Xu ◽  
Chang-Hwan Choi
Keyword(s):  
Rate Constants ◽  
Water Droplet ◽  
Evaporation Rate ◽  
Pure Water ◽  
Hydrophobic Surface ◽  
Superhydrophobic Surfaces ◽  
Clear Correlation ◽  
Planar Surface ◽  
Kinetics Of ◽  
Evaporation Kinetics

In this paper, the evaporation kinetics of microliter-sized sessile droplets of gold colloids (∼250 nm in particle diameters) was experimentally studied on micropatterned superhydrophobic surfaces, compared with those of pure water on a planar hydrophobic surface. The structural microtopography of superhydrophobic surfaces was designed to have a constant air fraction (∼0.8) but varying array patterns including pillars, lines, and wells. During evaporation in a room condition, the superhydrophobic surfaces exhibited a stronger pinning effect than a planar surface, especially in the initial evaporation stage, with significant variations by the surface topographies. Compared to a pure water droplet, colloids exhibited further promoted pinning effects, mainly in the later stage of evaporation. While the well-known evaporative mass transport law of sessile droplets (i.e., linear law of “V2/3∝t”) was generally applicable to the superhydrophobic surfaces, much smaller evaporation rate constants were measured on the patterned superhydrophobic surfaces than on a planar hydrophobic surface. A colloidal droplet further showed lower evaporation rate constants than a pure water droplet as the concentration of particles in the droplets increased over the evaporation. Such transition was more dramatic on a planar surface than on the micropatterned surfaces. Whereas there was no clear correlation between evaporation mode and the evaporation rate observed on the superhydrophobic surfaces, the prominent decrease of the evaporation rate on the planar hydrophobic surface was accompanied with the onset of a second pinning mode.

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